1. Field of the Invention
The invention relates to a video transcoding method of transcoding a bit stream of a first video encoding format into a bit stream of a second video encoding format, and a video transcoding apparatus which transcodes a bit stream of a first video encoding format into a bit stream of a second video encoding format.
2. Description of the Related Art
As an international standard method of video encoding, MPEG-1, MPEG-2, and MPEG-4 of ISO/IEC JTC1/SC29/WG11 are known. These encoding methods differ in a video encoding data format from one another. The technology of transforming the bit stream at high speed between such different encoding video data formats is known as a video transcoding technology. This transcoding technology is a re-encoding which once decodes an encoded bit stream and again encodes the decoded bit stream.
In a conventional video transcoding apparatus which transcodes an MPEG-2 format to an MPEG-4 format, the MPEG-2 stream stored in an MPEG-2 stream storage device is decoded by an MPEG-2 decoder.
Generally, the video signal decoded by an MPEG-2 decoder and the video signal encoded by an MPEG-4 encoder differ in a screen size from each other. For this reason, the screen size of the video signal decoded by the MPEG-2 decoder is converted by a screen size converter.
The MPEG-4 encoder encodes the video data from the size converter in the MPEG-4 format to generate an MPEG-4 encoded stream, and stores the MPEG-4 encoded stream in a storage device. At this time, the encoder detects motion vectors of the video data, and the video data is reconstructed based on the motion vectors.
Thus, in the conventional transcoding technology, when transcoding the bit stream from MPEG-2 format to MPEG-4 format, the processing for detecting the motion vector must be executed. For this reason, a long time is required for transcoding the encoding format.